Thermal, rheological and mechanical properties of poly(propylene carbonate)/methyl methacrylate-butadiene-styrene blends

Different amounts of core-shell methyl methacrylate-butadiene-styrene (MBS) impact modifiers were incorporated into biodegradable poly(propylene carbonate) (PPC) in a batch mixer, aiming at improving the mechanical properties and raising the glass transition temperature (T-g) of PPC. A series of properties, such as thermal behavior, miscibility, rheological and mechanical properties, and the morphological analysis of PPC/MBS blends were investigated in detail. PPC was partially miscible with MBS according to the results of dynamic mechanical analysis tests which showed a little shift in the peaks associated with the glass transition temperatures. The differential scanning calorimetry results showed that the T-g of PPC increased gradually as MBS content increased. Additionally, the thermal stability properties of the blends were improved dramatically. The rheological properties obtained by the melt flow index tests indicated that the melting viscosities of PPC/MBS blends increased with the addition of MBS, and all melting viscosities of the polymer blends were higher than those of pure PPC. The mechanical properties of PPC/MBS blends implied that the elongation at break increased from 5.3 % of pure PPC to 52 % after incorporation of 20 % MBS into the blends. Accordingly, the impact test results indicated that MBS could toughen the PPC matrix effectively, about 3.7 times higher compared to pure PPC. The scanning electron microscopy studies on PPC/MBS blends showed that MBS particles were dispersed well in the PPC matrix when MBS content was below 10 %, whereas the aggregation could be clearly seen when the content of MBS was over 15 %.